The present invention relates to a process for producing an information recording material and a coating solution for use therein. More specifically, the present invention relates to a process for well productively producing an information recording material such as a thermal recording material or an inkjet recording material excellent particularly in the quality of coating layers and excellent in various properties, and a coating solution for use in this process.
Information recording materials having an information-recording layer formed on a substrate are used in broad fields. A variety of recording materials such as a pressure-sensitive recording material, a heat-sensitive recording material, a photo-sensitive heat-sensitive recording material, a photo-sensitive pressure-sensitive recording material, a thermal transfer recording material, an inkjet recording material, etc., are practically used as such information recording materials. In recent years, information recording materials having two or more layers formed on a substrate are also used to comply with demands for higher functions and higher performances.
A thermal recording material is generally a material in which a heat-sensitive recording layer containing a thermally color-formable material is formed on a substrate. The thermal recording material is heated with a thermal head (hot head), a thermal pen, laser light, or the like, to form an image.
The above thermal recording material is advantageous in that a recording can be obtained with a relatively simple unit, that maintenance is easy and that no noise is made, so that it is widely used in the fields of measuring recorders, facsimile machines, printing machines, computer terminals, labels, automatic vending machines of tickets, etc. In recent years, further, for attaining superior color density and sensitivity, image stability and tones of a plurality of colors, there are practically used thermal recording materials having at least one protective layer or undercoat layer or both and two or more heat-sensitive recording layers, in addition to a thermal recording material having a single heat-sensitive recording layer alone.
An inkjet recording method is a method in which fine globules of an ink are ejected from an inkjet recording device and allowed to adhere to an inkjet recording material to form an image or letters. As the above inkjet recording material, a material such as a non-coated paper having no ink receptor layer is sometimes used. However, an ink receptor layer is formed on a substrate for use when printing is made on a synthetic resin film having no ink-reception properties or when it is intended to obtain a finer image. With diversification in use, color imaging or higher performances such as faster printing in recent years, a larger amount of an ink is ejected, and a higher-capacity ink absorption and a higher print density come to be required. Since no sufficient performances for the above requirements can be obtained with any conventional single ink receptor layer, an inkjet recording material having two or more ink receptor layers are practically used as well.
In a conventional information recording material having two or more layers laminated on a substrate, each layer is independently formed by application and drying to form the laminated layers, and the application is carried out by a method such as an air knife coating method, a blade coating method, a rod coating method or a reverse roll coating method. However, an information recording material prepared by any one of the above methods has problems that the quality of coating layers is poor, that an upper layer has pin holes caused by infiltration of an upper layer coating solution into a lower layer and repellency during application to form the upper layer and that the quality varies due to continuous coating for a long period of time. Moreover, there are problems in a limit to application at a high rate and a decrease in productivity due to application procedures to be carried out a plurality of times.
As compared with these methods, the curtain coating method disclosed in Japanese Patent Publication No. 49-24133, etc., is a method in which a free-fall curtain of a coating solution is formed and allowed to collide with a substrate to apply the coating solution to the substrate, and it is known that the curtain coating method achieves a good quality of coating layers and has suitability to application at a high rate. Further, since a plurality of layers can be simultaneously formed by curtain-coating of a coating composition film formed of a plurality of coating solution layers, the productivity in multi-layer application can be improved to a great extent. In the simultaneous multi-layer application using a curtain coating method, the coating composition film made of a plurality of coating solution layers is formed, and thereafter, it is required to dry the coating composition film to solidness without disturbing the layer structure thereof. When the layer structure is disturbed to cause an intermingling of layers, the layers comes to exhibit no sufficient functions thereof, so that an information recording material is degraded in various properties. In the field of conventional photographic photosensitive materials prepared by simultaneous multi-layer application using a curtain coating method, generally, each coating solution contains gelatin as a binder, and coating composition layers are cooled immediately after coating composition solutions are transferred onto a substrate, so that the coating solutions are immobilized by gelling of the gelatin therein, whereby no intermingling of the layers takes place.
In the information recording material, for example, in a heat-sensitive recording material, there is a problem that addition of gelatin sufficient for immobilizing coating solutions by cooling degrades various properties such as color-formability, image stability, etc., to a great extent. An inkjet recording material involves problems that no sufficient ink absorption capacity or absorption rate can be obtained. Further, there has been found no method of immobilizing coating solutions with any other substance than gelatin without impairing the above properties, and it is not yet possible to prevent the intermingling of layers by a method similar to the method employed for a photographic photosensitive material.
Meanwhile, unlike a photographic photosensitive material, most of information recording materials use a substrate having a very high water absorbing property such as paper, and a layer having a high water absorbing property is pre-coated on a substrate in many cases. When a coating composition film made of a plurality of layers of coating solutions is curtain-coated on such a substrate, water in the coating solution of the lowermost layer constituting the above coating composition film migrates into the substrate or a layer pre-coated on the substrate, and water in the coating solution of one upper layer accordingly migrates into another lower layer. The problem is that non-water components contained in layers also migrate from one upper layer to another lower layer due to the migration of water and cause the intermingling of layers.
It is a first object of the present invention to overcome the above drawbacks of prior art and provide a process for efficiently producing an information recording material such as a heat-sensitive recording material, an inkjet recording material, or the like, which is particularly excellent in the quality of coating layers and excellent in various properties.
It is a second object of the present invention to provide coating solutions suitable for use in the above process.
The present inventors have made diligent studies for achieving the above objects, and as a result, in the process for the production of an information recording material having an information recording layer formed on a substrate, it has been found that the first object can be achieved by
(1) curtain-coating a coating composition film comprising two coating solution films that come to have a high viscosity when brought into contact, or mixed, with each other and an intermediate coating solution film that is for isolating said two coating solution films one from the other and is provided between said two coating solution films, to form the information recording layer;
(2) curtain-coating a coating composition film made of a plurality of layers to form part or the entirety of a plurality of layers constituting the information recording material, wherein at least one set of adjacent two layers constituting the coating composition film made of a plurality of layers to be curtain-coated has a constitution in which the viscosity of the adjacent two layers increases with the passage of time when the two layers are brought into contact, or mixed, with each other;
(3) curtain-coating a coating composition film made of a plurality of layers to form part or the entirety of a plurality of layers constituting the information recording material, wherein water or an aqueous liquid is applied to a substrate surface on which said coating composition film is to be formed, and immediately thereafter said coating composition film is curtain-coated in a non-dry state of the substrate to form the information recording layer; or
(4) curtain-coating a coating composition film made of a plurality of layers to form part or the entirety of a plurality of layers constituting the information recording material, wherein a coating solution containing at least 90% by weight of water on the basis of the total weight of said coating solution is used as a coating solution for a lowermost layer constituting said coating composition film made of a plurality of layers to be curtain-coated.
Further, it has been found that the second object can be achieved by a combination of three coating solutions having specific properties, which are for use in the above process (1), and a combination of two coating solutions having specific properties, which are for use in the above process (2).
The present invention has been completed on the basis of the above findings.
That is, the present invention provides,
(1) a process for producing an information recording material having an information recording layer formed on a substrate, which comprises curtain-coating a coating composition film made of a plurality of layers on the substrate to form the information recording layer,
said coating composition film comprising two coating solution films of which the viscosity increases when they are brought into contact, or mixed, with each other and an intermediate coating solution film that is for isolating said two coating solution films one from the other and is provided between said two coating solution films (to be referred to as xe2x80x9cproduction process Ixe2x80x9d hereinafter),
(2) a process for producing an information recording material having an information recording layer formed on a substrate, which comprises curtain-coating a coating composition film made of a plurality of layers to form part or the entirety of a plurality of layers constituting the information recording material,
said coating composition film comprising at least one set of adjacent two layers of which the viscosity increases with the passage of time when they are brought into contact, or mixed, with each other (to be referred to as xe2x80x9cproduction process IIxe2x80x9d hereinafter),
(3) a process for producing an information recording material having an information recording layer formed on a substrate, which comprises curtain-coating a coating composition film made of a plurality of layers to form part or the entirety of a plurality of layers constituting the information recording material,
wherein water or an aqueous liquid is applied to a substrate surface on which said coating composition film is to be formed, and immediately thereafter said coating composition film is curtain-coated in a non-dry state of the substrate to form the information recording layer (to be referred to as xe2x80x9cproduction process IIIxe2x80x9d hereinafter),
(4) a process for producing an information recording material having an information recording layer formed on a substrate, which comprises curtain-coating a coating composition film made of a plurality of layers to form part or the entirety of a plurality of layers constituting the information recording material,
wherein a coating solution of a lowermost layer constituting the coating composition film made of a plurality of layers to be curtain-coated contains at least 90% by weight, based on the total weight of said coating solution, of water (to be referred to as xe2x80x9cproduction process IVxe2x80x9d hereinafter),
(5) coating solutions for use in the above production process I, which are a combination of two coating solutions of which the viscosity increases when the two coating solutions are brought into contact, or mixed, with each other, with a coating solution that is for use as an intermediate coating solution for isolating the two coating solutions and shows no increase in viscosity when brought into contact, or mixed, with either of the two coating solutions (to be referred to as xe2x80x9ccoating solutions Ixe2x80x9d hereinafter), and
(6) coating solutions for use in the above production process II, which are a combination of two coating solutions of which the viscosity increases with the passage of time when the two coating solutions are brought into contact, or mixed, with each other (to be referred to as xe2x80x9ccoating solutions IIxe2x80x9d hereinafter).
The term xe2x80x9ccoating solutionxe2x80x9d includes dispersions of solid particles in a liquid, depending upon the ingredients contained therein.
In the process for producing an information recording material in the present invention, part or the entirety of a plurality of layers constituting the information recording material are formed by curtain-coating a coating composition film made of a plurality of layers and then drying it. The layers to be formed by curtain-coating are not specially limited in kind. Examples of such layers in a heat-sensitive recording material include an undercoat layer, a heat-sensitive recording layer, a protective layer, and the like, and examples of such layers in an inkjet recording material include an undercoat layer, an ink receptor layer, and the like. A combination of these adjacent layers are together simultaneously applied by curtain-coating. Specific examples of a combination of the layers that are simultaneously applied in a heat-sensitive recording material includes a combination of an undercoat layer and a heat-sensitive recording layer, a combination of a heat-sensitive recording layer and a protective layer, a combination of an undercoat layer, a heat-sensitive recording layer and a protective layer, a combination of two or more different undercoat layers, a combination of two or more different heat-sensitive recording layers and a combination of two or more different protective layers. Specific examples of such a combination in an inkjet recording material include a combination of an undercoat layer and an ink receptor layer and a combination of a plurality of ink receptor layers, while there is no special limitation to be imposed on other combinations.
Although not specially limited, an applicator machine for forming the coating composition film made of a plurality of coating solution layers on a substrate includes an extrusion hopper type curtain coater and a slide hopper type curtain coater. The slide hopper type curtain coater disclosed in Japanese patent Publication No. 49-24133, which is for use for forming a photographic photosensitive material, etc., is particularly preferably used. This slide hopper type curtain coater makes it easier to apply the coating composition film made of a plurality of layers.
When general coating solutions for an information recording material are applied with the above curtain coater to form a plurality of layers constituting an information recording material, these coating solutions do not undergo gelling and immobilization unlike coating solutions for a photographic photosensitive material, so that intermingling of layers gradually proceeds immediately after application until drying completes. If intermingling of layers takes place, the layers cannot exhibit sufficient performances, and there can be obtained no information recording material excellent in various properties. For example, in a heat-sensitive recording material, when an undercoat layer and a heat-sensitive recording layer are formed by simultaneous multi-layer application according to curtain coating and when the undercoat layer and heat-sensitive recording layer undergo intermingling, the color density decreases. When a heat-sensitive recording layer and a protective layer are formed by simultaneous multi-layer application according to curtain coating and when the heat-sensitive recording layer and the protective layer undergoes intermingling, there are caused problems of a decrease in color density, a decrease in barrier properties of the protective layer and a difficulty in printing. In an inkjet recording material, further, when a plurality of ink receptor layers undergo intermingling, the color density decreases, and the ink absorption capacity and the ink absorption rate decrease. If such an intermingling of layers takes place, the layers cannot exhibit sufficient functions.
The process for producing an information recording material in the present invention includes four embodiments, the following production processes I to IV, for preventing the above intermingling of layers. Each production process will be explained below.
First, in the production process I of an information recording material in the present invention, for preventing the intermingling of layers, a coating composition film made of a plurality of layers is curtain-coated on a substrate, said a coating composition film comprising two coating solution films of which the viscosity increases when the two coating solution films are brought into contact, or mixed, with each other and an intermediate coating solution film that is for isolating said two coating solution films one from the other and is provided between said two coating solution films, and the applied coating composition film is dried. As inter-mixing of layers during drying proceeds, the two layers sandwiching the intermediate coating solution layer comes to be partially mixed with the intermediate coating solution layer, and as the inter-mixing further proceeds, the intermediate coating solution layer and the two layers sandwiching the intermediate coating solution layer comes to be in a partially mixed state to have a high viscosity. Further inter-mixing of the layers is therefore inhibited, and although the two coating solution films of which the viscosity increases when they are brought into contact, or mixed, with each other are partially mixed, major parts of these layers are not at all mixed, so that the layers can exhibit their sufficient functions.
The intermediate coating solution in the production process of the information recording material in the present invention is used for preventing the two coating solutions sandwiching the intermediate coating solution layer from coming into contact, or getting mixed, with each other to have a high viscosity before the coating composition film is applied to a substrate. The intermediate coating solution is therefore required not to show an increase in viscosity when it comes in contact, or gets mixed, with any one of the two coating solutions sandwiching the intermediate coating solution layer. Further, the intermediate coating solution is also required not to prevent an increase in viscosity when the two coating solutions sandwiching the intermediate coating solution layer comes into contact, or get mixed, with each other. Any intermediate coating solution can be used without any special limitation so long as it has the above properties and suitability to curtain-coating. Further, preferably, the intermediate coating solution does not prevent functions of the two coating solutions sandwiching the intermediate coating solution layer.
When curtain-coating is carried out in a state where two coating solution layers of which the viscosity increases when brought into contact, or mixed, with each other are in contact without providing the intermediate coating solution layer, the two coating solutions increase in viscosity, or if the curtain-coating is possible, the constitution of layers is disturbed. Further, when the intermediate coating solution layer has an insufficient thickness, a similar phenomenon takes place, so that the intermediate layer is required to have a sufficient thickness for preventing a contact between the two coating solution layers before they are applied to a substrate.
The two coating solutions that are used with the intermediate coating solution layer sandwiched between them and show an increase in viscosity when brought into contact, or mixed, with each other are not specially limited. When the two coating solutions that are to be applied with the intermediate coating solution layer sandwiched between them have no function of increasing in viscosity when brought into contact, or mixed, with each other, proper additives can be incorporated into these two coating solutions, respectively, so that the coating solutions can exhibit the function of increasing in viscosity when brought into contact, or mixed, with each other.
The combination of the additives to be incorporated into the two coating solutions for attaining an increase in viscosity when the two coating solutions are brought into contact, or mixed, with each other includes a combination of a positively charged polymer compound with a negatively charged low-molecular-weight compound, a combination of a negatively charged polymer compound with a positively charged low-molecular-weight compound, a combination of a positively charged polymer compound with a negatively charged polymer compound, a positively charged low-molecular-weight compound with a negatively charged low-molecular-weight compound, and a combination of a polyvalent metal ion with a polymer compound that is insolubilized upon a reaction with it, although the above combination shall not be limited thereto.
The positively charged polymer compound includes an oligomer and a polymer of primary to tertiary amines and quaternary ammonium salt. Specific examples thereof include a dimethylamine-epichlorohydrin condensate, an acrylamidediallylamine copolymer, a polyvinylamine polymer, chitosan, and salts of these, while the positively charged polymer compound shall not be limited thereto.
The negatively charged polymer compound includes an oligomer and a polymer containing a carboxyl group, a sulfone group or a sulfino group. Specific examples thereof include polyacrylic acid, a acrylate copolymer, polymethacrylic acid, methacrylate copolymer, polyvinylsufonic acid, a vinylsulfonate copolymer, polyvinylsulfinic acid, alginic acid, carageenan, pectin, furcellaran, carboxymethylcellulose, heparin, chondroitin sulfate, xanthan gum, gum Arabic, guar gum and salts of these, while the negatively charged polymer compound shall not be limited thereto.
The polymer compound that is insolubilized upon a reaction with a polyvalent metal ion includes, for example, alginic acid, carboxymethylcellulose, pectin and salts of these, while above polymer compound shall not be limited thereto.
The negatively charged low-molecular-weight compound includes, for example, inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid, and organic acids such as carboxylic acids, sulfonic acids and sulfinic acids, while the above compound shall not be limited thereto.
The positively charged low-molecular-weight compound includes, for example, inorganic bases such as sodium hydroxide, potassium hydroxide and ammonia, and organic bases such as primary to tertiary amines or quaternary ammonium salts, e.g. dicyandiamide or dimethyldiallyl-ammonium chloride, although the above compound shall not be limited thereto.
The polyvalent metal ion includes, for example, calcium ion, magnesium ion, aluminum ion, zinc ion, boron ion and iron ion, while the polyvalent metal ion shall not be limited thereto.
Preferably, the additives to the coating solutions for causing the viscosity of the two coating solutions to increase when brought into contact, or mixed, with each other can attain a higher viscosity when they are added in a smaller amount. Further, preferably, the additives can attain a high viscosity in a shorter period of time after the two coating solutions are brought into contact, or mixed, with each other.
The coating solutions I of the present invention are coating solutions for use in the above production process I and are a combination of two coating solutions of which the viscosity increases when the two coating solutions are brought into contact, or mixed, with each other, with a coating solution that is for use as an intermediate coating solution for isolating the two coating solutions and shows no increase in viscosity when brought into contact, or mixed, with either of the two coating solutions.
Preferably, the two coating solutions of which the viscosity increases when brought into contact, or mixed, with each other respectively contain, as additives, a positively charged polymer compound and a negatively charged low-molecular-weight compound in combination, a negatively charged polymer compound and a positively charged low-molecular-weight compound in combination, a positively charged polymer compound and a negatively charged polymer compound in combination, a positively charged low-molecular-weight compound and a negatively charged low-molecular-weight compound in combination, or a polyvalent metal ion and a polymer compound that is insolubilized upon a reaction with it in combination,
In the production process II of an information recording material in the present invention, at least one set of two adjacent layers constituting a coating composition film made of a plurality of layers for curtain-coating are prepared so as to increase in viscosity with the passage of time when brought into contact, or mixed, with each other, and the coating composition film is applied. The two adjacent layers that increase in viscosity with the passage of time when brought into contact, or mixed, with each other are required to gradually increase in viscosity with the passage of time after brought into contact, or mixed, with each other. When the two layers instantly have a high viscosity upon contact or mixing, the layer constitution of the coating composition film is disturbed after the coating composition film made of a plurality of layers is formed and before it is applied to a substrate, or the coating composition film per se cannot be formed. It is therefore required to adjust the rate and degree of an increase in viscosity which increase takes place after the above two layers are brought into contact, or mixed, with each other, in conformity with coating solutions and an applicator machine, such that the layer constitution is not disturbed before application of the coating composition film on a substrate. After application of the coating composition film to a substrate, an increase in viscosity proceeds due to the contact or mixing, and most parts of these layers undergo no mixing and show an excellent layers-separated state.
The combination of the coating solutions that gradually increase in viscosity after brought into contact, or mixed, with each other is not specially limited. Proper additives can be incorporated into the two coating solutions, respectively, so that the coating solutions can exhibit the function of gradually increasing in viscosity when brought into contact, or mixed, with each other.
The combination of the additives that are incorporated into the coating solutions for gradually increasing the viscosity of the two coating solutions with the passage of time after their contact or mixing specifically includes, for example, a combination of an alkali and an emulsion of a carboxyl-group-containing polymer that is soluble upon a reaction with the alkali, while the above combination shall not be limited thereto.
The emulsion of a carboxyl-group-containing polymer soluble upon a reaction with an alkali includes an emulsion of a copolymer of acrylic acid, methacrylic acid, maleic acid or fumaric acid with other monomer. Such an emulsion exists as a water insoluble emulsion in an acidic-neutral region since the carboxyl group contained in the polymer has a low degree of dissociation and therefore has no solubility in water. When an alkali is added to the above emulsion, the carboxyl group is dissociated and the emulsion exhibits its solubility in water, so that the emulsion is gradually dissolved in water to cause a gradual increase in viscosity. The rate of an increase in viscosity can be controlled on the basis of the particle diameter of the emulsion and the content of the carboxyl group.
Preferably, the additives to the coating solutions for causing the viscosity of the two coating solutions to gradually increase with the passage of time after brought into contact, or mixed, with each other can attain a higher viscosity when they are added in a smaller amount.
When a plurality of layers for constituting an information recording material are applied by multi-layered simultaneous application with the above applicator machine for curtain-coating, generally, the surface tension of an uppermost layer coating solution is essentially adjusted to be equivalent to, or lower than, the surface tension of a lower layer coating solution in order to prevent a repellency phenomenon that the uppermost layer shrinks on the lower layer to cause a defect on the uppermost layer. The above uppermost layer refers to a layer farthest from a substrate, and the above lower layer refers to a layer nearer to the substrate. For adjusting the surface tension, there is employed a method in which surfactants are added to the coating solutions to decrease their surface tensions. On the other hand, it is very difficult to increase the surface tension of any coating solution, and such is not generally carried out. For the above purpose, it is necessary to add a larger amount of a surfactant to the uppermost layer coating solution in order to attain a lower surface tension. In an information recording material, for example, in a heat-sensitive recording material, addition of a large amount of a surfactant to the coating solutions involves drawbacks that the heat-sensitive recording material is degraded in various properties such as color forming and image stability and further that it is difficult to control the wettability of water and oil to the heat-sensitive recording material. In an inject recording material, the ink-absorbing capability and he print density are greatly susceptible to a surfactant, no intended quality may be obtained in some cases. The method of preventing repellency of the uppermost layer by adding a surfactant has a defect that the performances of an information recording material are limited as described above.
In the production process II of an information recording material in the present invention, the uppermost layer coating solution may have a higher surface tension than the adjacent lower layer coating solution. After the uppermost layer coating solution and the adjacent lower layer coating solution are brought into contact, or mixed, with each other, the viscosity thereof increases with the passage of time, whereby there can be prevented the repellency phenomenon that the uppermost layer shrinks on the lower layer.
The rate of an increase in viscosity of the upper layer coating solution and the adjacent lower layer coating solution after they are brought into contact, or mixed, with each other is required to be a rate sufficient for preventing the repellency phenomenon. For the above reasons, it is required to adjust the rate and degree of an increase in viscosity which increase takes place after the above two layers are brought into contact, or mixed, with each other, in conformity with to coating solutions and an applicator machine, such that the repellency phenomenon can be prevented and that the layer constitution is not disturbed before application of the coating composition film to a substrate.
The coating solutions II of the present invention are used in the above production process II and are a combination of two coating solutions which increase in viscosity with the passage of time when brought into contact, or mixed, with each other. Preferably, one of the above two coating solutions contains an emulsion of a carboxyl-group-containing polymer soluble upon a reaction with an alkali, and the other contains an alkali, so that the emulsion and the alkali are combined. Further, suitably, the two coating solutions are a combination of two coating solutions having different surface tensions.
In the production process III of an information recording material in the present invention, for preventing intermingling of layers, water or an aqueous liquid is applied to a substrate in advance so that the substrate absorbs water before curtain-coating, and after such is completed, the curtain-coating is carried out. By the above operation, shifting of water into the substrate side is suppressed when the curtain-coating is carried out, and a major part of the applied layers are not at all intermingled and show an excellent layer-separated state.
In the present invention, the curtain-coating is carried out with a curtain-coating applicator machine to form a coating composition film. Before the coating composition film is formed, water or an aqueous liquid is applied to the substrate surface on which the coating composition film is to be formed. As a liquid to be applied, water alone may be used. However, an aqueous liquid containing a material soluble or dispersible in water is preferred.
Although not specially limited, examples of the above material soluble or dispersible in water are as follows.
The above materials include water-soluble polymers such as a starch polymer, a polyvinyl alcohol polymer, a gelatin polymer, a polyacrylamide polymer and a cellulose polymer, emulsions and latexes such as a petroleum resin emulsion, an emulsion or latex of a copolymer having at least components from ethylene and acrylic acid (or methacrylic acid), and an emulsion or latex of a styrene-butadiene, styrene-acrylate, vinyl acetate-acrylate, ethylene-vinyl acetate or butadiene-methyl methacrylate copolymer or a carboxy-modified copolymer of any one of these. Further, the coating solutions may contain an alkali metal salt such as sodium chloride or potassium chloride, an alkaline earth metal salt such as calcium chloride or barium chloride, a colloidal metal oxide such as colloidal silica, an organic antistatic agent such as polystyrenesulfonate, a pigment such as clay, kaolin, calcium carbonate, talc, barium sulfate or titanium oxide, a pH adjuster such as hydrochloric acid, phosphoric acid, citric acid or sodium hydroxide, and additives such as a coloring pigment, a coloring dye or a fluorescent brightener. The above materials may be used in combination as required.
In the above production process III, the machine for applying water or an aqueous liquid to a substrate surface is not specially limited. There may be used a generally known applicator machine. For example, it can be selected from coating machines according to different liquid application methods such as pressure fountain, jet fountain, flooded nip, roll metering, rod metering and curtain coaters, or application-amount-adjustable machines such as blade, rod, roll nip and air knife coaters. These coaters may be used in combination as required.
Further, in the production process IV of an information recording material in the present invention, a coating solution of a lowermost layer constituting the coating composition film made of a plurality of layers to be curtain-coated contains at least 90% by weight, based on the total weight of said coating solution, of water for preventing inter-mingling of layers. When the lowermost layer coating solution has a water content of at least 90% by weight based on the total weight of the said coating solution, shifting of water from an upper layer does not easily take place even if water in the lowermost layer coating solution moves to the substrate or an undercoat layer applied to the substrate beforehand, since the lowermost layer coating solution has a sufficient content of water, so that the upper layer is dried before the intermingling of layers proceeds and the intermingling of layers is prevented.
The lowermost layer coating solution is not specially limited so long as it contains at least 90% by weight, based on the total weight of the coating solution, of water. Therefore, the lowermost layer coating solution may be a coating solution essential for materializing the function of an information recording material, or it may be a layer that is provided for preventing the intermingling of layers but has no direct relationship to the function of an information recording material.
The lowermost layer coating solution preferably contains a component film-formable after drying, since shifting of water can be more effectively prevented. Specific examples of the component film-formable after drying include water-soluble polymers such as polyvinyl alcohols, starches, celluloses, polyacrylamides, an alkali salt of a styrene/maleic anhydride copolymer and an alkali salt of an ethylene/maleic anhydride copolymer, polyacrylic acid; and emulsions of synthetic resins such as polymethacrylic acid, polyacrylic ester, polymethacrylic ester, a styrene/butadiene copolymer, an acrylonitrile/butadiene copolymer, an ethylene/vinyl acetate copolymer, an acrylic acid amide/acrylic ester copolymer and an acrylic acid amide/acrylic ester/methacrylic acid terpolymer.
In the production processes I to IV of an information recording material in the present invention, the method of drying is not critical. Specifically, the drying method includes, for example, a method of blowing hot air, a method of blowing dry air, a method of irradiation with an infrared ray, a method of irradiation with microwave, and these methods may be used in combination.
In the production processes I to IV of an information recording material in the present invention, coating solutions of plurality of layers constituting the coating composition film to be applied are used after the viscosity and surface tension thereof are adjusted for decreasing the intermingling of layers during curtain-coating. When a viscosity difference among the layers is small, the degree of intermingling of layers is low. The viscosity difference among the layers is preferably 100 mPa.s or less. When the surface tension of one coating solution to form one lower layer is smaller than the surface tension of another coating solution to form an upper layer, undesirably, there occurs a phenomenon that the coating solution forming the upper layer is repelled on the coating solution forming the lower layer, and no uniform coating composition film is formed, so that the quality of a film formed by application is sometimes degraded. When these layers have the same surface tensions, desirably, the repellency phenomenon does not easily take place. When the surface tension of a coating solution to form an upper layer is adjusted to be smaller than the surface tension of a coating solution to form a lower layer, particularly desirably, an excellent quality of a film formed by application is obtained. When three or more layers are simultaneously applied, preferably, the surface tensions of these layers are adjusted such that the surface tension decreases successively in the order of from the lowermost layer, i.e., a layer nearest to a substrate to the uppermost layer that is farthest from the substrate. However, the above is not applicable to the surface tensions of the coating solution of the uppermost layer and the coating solution of the adjacent lower layer in the production process II of an information recording material in the present invention.
For adjusting the viscosities of the coating solutions, there may be employed a method of mixing a water-soluble polymer such as polyvinyl alcohol, starch or carboxymethylcellulose, or a thickener such as an acrylic emulsion with a coating solution to increase the viscosity thereof, a method of increasing a solid content in a coating solution to increase the viscosity or a method of diluting a coating solution to decrease the viscosity.
For adjusting the surface tensions of the coating solutions, any amount of an anionic surfactant such as carboxylic acid salt, sulfonic acid salt, sulfuric ester salt or phosphoric ester salt, a nonionic surfactant such as an ether type, ether-ester type, ester type or nitrogen-containing surfactant or an amphoteric surfactant such as betain, aminocarboxylic acid salt or an imidazoline derivative may be mixed with the coating solutions.
In the production processes I to IV of an information recording material in the present invention, the coating solutions of a plurality of layers constituting the coating composition film to be applied may contain a pigment dispersing agent, a thickener, a fluidity improver, an anti-foaming agent, a foaming suppressor, a release agent, a foaming agent, a penetrating agent, a coloring dye, a coloring pigment, a fluorescent brightener, an anti-oxidant, an antiseptic agent, a mildewproofing agent, a water-resistance-imparting agent, a wet strength agent, a dry strength agent, etc., as required.
Each layer of an information recording material produced in each of the production processes I to IV in the present invention may contain an optional binder. Specific examples of the binder include starches, hydroxyethylcellulose, methylcellulose, ethylcellulose, carboxymethylcellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyacrylic ester, polymethacrylic ester, sodium polyacrylate, polyethylene terephthalate, polybutylene terephthalate, chlorinated polyether, an allyl resin, a furan resin, a ketone resin, oxybenzoyl polyester, polyacetal, polyether ether ketone, polyether sulfone, polyimide, polyamide, polyamideimide, polyaminobismaleimide, polymethylpentene, polyphenylene oxide, polyphenylene sulfide, polyphenylene sulfone, polysulfone, polyarylate, polyallylsulfone, polybutadiene, polycarbonate, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyurethane, a phenolic resin, a urea resin, a melamine resin, a melamine formalin resin, a benzoguanamine resin, a bismaleimide triazine resin, an alkyd resin, an amino resin, an epoxy resin, an unsaturated polyester resin, a styrene/butadiene copolymer, an acrylonitrile/butadiene copolymer, a methyl acrylate/butadiene copolymer, an ethylene/vinyl acetate copolymer, an acrylic acid amide/acrylic ester copolymer, an acrylic acid amide/acrylic ester/methacrylic acid terpolymer, an alkali salt of a styrene/maleic anhydride copolymer, an alkali salt or ammonium salt of an ethylene/maleic anhydride copolymer and other various polyolefin resins. These binders may be used alone or as a mixture containing at least two binders of these.
The substrate for use in the information recording material to be produced by any one of the production processes I to IV of an information recording material in the present invention may be any one of transparent, semi-transparent and opaque substrates. The above substrate can be selected from paper, various non-woven fabrics, woven fabrics, a synthetic resin film, a synthetic resin laminated sheet, a synthetic paper, a metal foil, a ceramic sheet, a glass sheet or a composite sheet made of a combination thereof as required depending upon a purpose, while the substrate shall not be limited thereto.
Any layer of an information recording material produced by any one of the production processes I to IV of an information recording material in the present invention may contain inorganic and organic pigments such as diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide and a urea-formalin resin as required. In addition to these, it may also contain higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as paraffin, paraffin oxide, polyethylene, polyethylene oxide, stearic acid amide and castor wax, a dispersing agent such as sodium dioctylsulfosuccinate, a surfactant and a fluorescent dye as required.
Further, an antioxidant and an ultraviolet absorbent may be incorporated for improving the information recording material in light resistance. Examples of the antioxidant include a hindered-amine-containing antioxidant, a hindered-phenol-containing antioxidant and a sulfide-containing antioxidant, while the antioxidant shall not be limited thereto. Examples of the ultraviolet absorbent include organic ultraviolet absorbents such as a benzotriazole ultraviolet absorbent, a salicylic acid ultraviolet absorbent and a benzophenone ultraviolet absorbent, and inorganic ultraviolet absorbents such as zinc oxide, titanium oxide and cerium oxide, while the ultraviolet absorbent shall not be limited thereto.
In a heat-sensitive recording material produced by any one of the production processes I to IV of an information recording material in the present invention, a component that forms a color by heating is not specially limited. Examples of the above component includes a combination of a generally colorless or light-colored electron-donating dye precursor with an electron-accepting compound, a combination of an aromatic isocyanate compound with an imino compound, a combination of a generally colorless or light-colored electron-donating dye precursor with an aromatic isocyanate compound, a combination of a metallic compound with a coordination compound and a combination of a diazonium salt with a coupler. In view of excellence in various properties such as color formability and image stability, it is particularly preferred to use a combination of a generally colorless or light-colored electron-donating dye precursor with an electron-accepting compound, a combination of an aromatic isocyanate compound with an imino compound or a combination of a generally colorless or light-colored electron-donating dye precursor with an aromatic isocyanate compound.
In a heat-sensitive recording material produced by any one of the production processes I to IV of an information recording material in the present invention, any layer of the heat-sensitive recording material may contain a material capable of electrically, magnetically or optically recording information. A surface provided with a heat-sensitive recording layer or a surface opposite thereto may be imparted with the capability of receiving an inkjet recording ink. Further, a surface opposite to a surface provided with a heat-sensitive recording layer may be provided with a back-coating layer for preventing curling or electrostatic charge, and further, this surface may be processed to impart it with adhesiveness. Further, printing with a UV ink, etc., may be carried out on the surface of a heat-sensitive recording layer.
In a heat-sensitive recording material produced by any one of the production processes I to IV of an information recording material in the present invention, any layer of the heat-sensitive recording material and the substrate may contain a light-heat converting material for printing with laser light.
In an inkjet recording material produced by any one of the production processes I to IV of an information recording material in the present invention, both surfaces of a substrate may be provided with an ink receptor layer. Any layer of the inkjet recording material may contain a material capable of electrically, magnetically or optically recording information. Further, a surface opposite to a surface provided with an ink receptor layer may be provided with a back-coating layer for preventing curling or electrostatic charge, and further, this surface may be processed to impart it with adhesiveness.
The present invention will be explained with reference to Examples hereinafter, while the present invention shall not be limited to these Examples. In Examples, xe2x80x9cpartxe2x80x9d stands for xe2x80x9cpart by weightxe2x80x9d and xe2x80x9c%xe2x80x9d stands for xe2x80x9c% by weightxe2x80x9d unless otherwise specified.